HTML5 Sea Map?

I'm not sure if this is actually a bug or not, so I'm just asking; should the mapper work at sea? It works on land, obviously, and very well for the Wilderness map. I get the feeling that the map SHOULD work, because every time I hit QL or just LOOK on a ship, I get a flash of the current sea map, but for the most part I just get a black box with "NO MAP AVAILABLE". Is this supposed to happen?